Using microartifacts to infer Middle Pleistocene lifeways at Schöningen, Germany

While archeologists usually favor the study of large and diagnostic lithic artifacts, this study illustrates the invaluable contribution of lithic microartifacts for interpreting hominin lifeways. Across a 64 m2 area of the Middle Pleistocene lakeshore site of Schöningen 13 II-3 in Northern Germany, we recovered a total of 57 small and micro flint artifacts, four small debris pieces, three natural fragments and three bone retouchers in close association with the skeleton of an extinct Eurasian straight-tusked elephant (Palaeoloxodon antiquus). This area lacks the type of formal knapped stone tools that would normally constitute the focus of archeological interpretations. By adopting a holistic approach, including morpho-technical analysis, experimental archeology, and use-wear and residue analyses, we demonstrate that these small and microartifacts are resharpening flakes that tell the story of the site. Fifteen resharpening flakes preserve microwear traces of processing wood. Microscopic residues of wood adhered to the former working edges of the tools corroborate this observation. Additionally, hominins used a sharp-edged, natural fragment of flint to process fresh animal tissue, which likely originates from the butchery of the elephant. These results provide unique, 300,000-year-old evidence for the functionally interconnected use of lithic, osseous and wood technologies. Furthermore, we document in-situ transformations of stone tools and the presence of both curational and expedient behaviors, thereby demonstrating the temporal depth of hominin activities at the lakeshore where the elephant died, and in the broader landscape as a whole.

Between 2017-2020, in an area corresponding to ca. 64 m 2 , we discovered an almost complete skeleton of an extinct Eurasian straight-tusked elephant in the silting event 3, layers 3b, 3bc and the upper surface of Schöningen 13 II-2a (preliminary study 30 , Supplementary Fig. 1, middle and right pictures). In that area, we recovered several dozen small and microartifacts, most of them between 5 and <15 mm, along with 4 pieces of angular debris and 3 natural fragments. Although it may seem that the sample is scarce, we would like to point out that, over the years, we have always taken the exact same care in excavating, water screening and analysing the sediments, and no lithics have been found in Schöningen 13 II-3. Hominin activity is also testified on the spot by three bone retouchers used for flint knapping, two of which refit together but were used as two separate tools (Ivo Verheijen, pers. comm.). Many of these artifacts were found among the elephant's bones, while others were lying in the immediate vicinity of the skeleton. The elephant has not been comprehensively studied yet, there are numerous bones undergoing restoration and zooarcheological analyses are still in process. A specific article on this elephant is in preparation. The area with the elephant represents a single, limited event in time and space. This peculiarity along with the pristine conditions of the recovered finds makes Schöningen 13 II-3 a key site for providing a high-resolution picture of hominin behavior during the Middle Pleistocene.

The experimental program
The archeological interpretations were supported by the results of a specific experimental program designed at studying the morphological attributes and distribution patterns of techno-functional microwear and microresidues on the resharpening flakes.

Experimental design
The locality of Schöningen is a complex of sites with a low density of lithic artifacts, in many cases, appearing as isolated finds, with the exception of a richer accumulation at the Spear Horizon 22 . At the elephant area in Schö 13 II-3, we did not recover any tools matching the microdebitage found around the carcass. However, since scrapers are common across the broader site complex, especially at Schö 13 II-4, we decided to produce and use scraper replicas to analyze the microdebitage produced by their resharpening. This choice was also dictated by the preliminary traceological results on the microdebitage, suggesting the performing of scraping activities. One of the authors (RW) produced the experimental scrapers using high-quality, fine-grained Baltic flint collected on the coast of northern Germany. After use, the scrapers were resharpened by the same flintknapper. The experiments were designed to process materials and perform activities that were most likely a part of the daily life of the Schöningen hominins. The scrapers were manually used by FV for a minimum of 60 minutes for scraping tasks, except for one tool used by combining transversal and longitudinal motions for 30 minutes ( Supplementary Fig. 10). In our experimental protocol, we included different animal and vegetal materials in both dry and fresh conditions (Supplementary Table 8 and Supplementary Fig. 10). As a reference, we also analyzed microwears on two flint replicas belonging to two different experimental programs and used to process wood (one scraper and one unretouched flake). Moreover, to create a control sample, we also examined microdebitage flakes from one unused scraper.
All of the experiments were performed under controlled conditions and all data were recorded. Once we concluded the practical activities, we observed the distribution of use-related residues on the scraper's active edges prior to resharpening at low magnifications.
Resharpening process and resharpening flakes The flintknapper RW resharpened the used scrapers by recreating the original scalar retouch identified on some archeological specimens. We did not impose any specific resharpening technique or gestures and we gave the knapper the freedom to follow their feeling according to the morphology of the active edge and the type of hammer used. We designed the experiments with the aim of testing soft and hard hammer percussion ( Supplementary Fig. 10). This also allowed us to record technological microtraces and residues produced by the different hammers. We used a dry horse metapodial as a soft, organic hammer (area on the epiphysis, Supplementary  Fig. 10i) and a boxwood billet ( Supplementary Fig. 10f) while two limestone hammerstones were used for testing hard hammer percussion ( Supplementary Fig. 10j). The recovery of three bone retouchers in the elephant area with embedded stone chips proved that soft hammering techniques were in use at Schö 13 II-3 30 . Embedded flint chips stuck in the bony tissues after repetitive blows were also recorded in our experimental trial, as shown in Supplementary Fig. 10h. We used only one type of hammer per each tool, except for one scraper that was resharpened using both wood and stone (see Supplementary Table 8). The choice of the hammer depended on the material worked by the tool. This means that we always used a hammer made of a different material than the one the scraper was used for. This has allowed us to easily recognize situations where technological residues overlapped with use-related ones 25 . We produced a total of 152 resharpening flakes on a total of 7 tools. The scrapers were considered fully resharpened when the whole dorsal active edge appeared fresh and without evidence of remaining used edge portion with visible use-traces or residues. For each scraper, we counted the total number of strokes necessary for complete resharpening, and we individually numbered and collected each resharpening flake after each strike. In several cases, more than one micro flake (up to 5) was removed with a unique stroke. We collected microflakes ≥ 2 mm in width to facilitate microwear analysis. Each flake was then placed in a clean plastic bag, awaiting microscopic analysis. The use-wear analysis was conducted using the optical equipment described in the Materials and Methods section in the main manuscript and available at the MCL at the University of Tübingen.

Results
In the next paragraphs we do not discuss the qualitative features of microwears and microresidues produced by working different materials with stone tools, these aspects being already extensively covered by several articles in the traceological literature 27,49,51,56,57,58,62,79,80 . Instead, we thought it would be more useful to discuss the location and distribution patterns of residues and wear traces on the microdebitage, being the two most relevant variables in the microscopic analysis of the resharpening flakes.
Residues: spatial patterns of distribution After resharpening, we first established the spatial distribution of microresidues on the resharpening flakes. For this purpose, we oriented the flakes according to the technological axis with their dorsal sides facing up, and we divided the dorsal face (the only face we recorded traces and residues) into three segments following the methodological protocol of Lombard 81 : 1) proximal, 2) mesial and 3) distal ( Supplementary Fig. 11). We thus recorded all microresidues and counted their occurrence in the above-mentioned segments. Clusters with large accumulations or very few fragmented residues were counted as a single occurrence (a note for a few accumulations was reported). In addition, we listed and recorded the platform as another potential area for residue accumulation. Although we are conscious that this method is not quantitatively reliable, our aim here is to monitor the incidence and distribution of technological and used-related microresidues regarding 1) the material worked/used and 2) the artifacts' surfaces. As a general impression, we noticed that organic residues accumulated more on the proximal segment of the resharpening flakes. Semi-dry hide and dry wood recorded the highest number of resharpening flakes with residues accumulated in this region, as shown in Supplementary Figs. 12 and 13. This is not surprising since it is the area in direct contact with the processed material. However, we recorded differences according to the material processed and its state of freshness. Within vegetal materials, fresh and dry wood seem to be inversely proportional: we recorded more residues on the mesial and distal segments of resharpening flakes in contact with fresh wood, while dry wood residues accumulated more on the proximal area. For the animal materials, the two scrapers used to process fresh skins also showed a reverse trend. Microflakes in contact with roe deer skin accumulated residues more in the distal area while those in contact with wild boar skin adhered to the proximal part. This may be due to the fact that the roe deer skin was wetter when processed, allowing residues to more easily slip away from the active edge of the tool during processing. Indeed, residues recorded on the microdebitage produced by the scraper used to process semi-dry hide accumulated more on the proximal area of flakes instead of on the mesial and distal ones. The distribution patterns of bone residues are instead distinctive with the occurrence of bony tissues mixed with collagen present only on the proximal segment. Finally, fresh animal tissues after butchery are more represented in the proximal area of the resharpening flakes. Microresidues also accumulated on the platform of several microflakes, with the highest number recorded for fresh skin and the lowest recorded for semi-dry hide. We recorded not only use-related residues but also technological residues produced by retouching the tools with different hammers, which were found mostly superimposed on the use-related residues ( Supplementary Fig. 14b,d,f). Occasionally, we found them disconnected as clearly distinguishable lines of deposition along the outer proximal edge ( Supplementary Fig. 14d). Technological residues also accumulated on the platform, mostly along the external platform edge. They often showed a random distribution, even though we observed hammer percussion residues in bands with a clear directionality, indicating the impact direction during resharpening (for an overview on this topic see 25 . Microwear: spatial patterns of distribution Microwear analysis of microdebitage is challenging. As reported by Chan and colleagues 18 , the interpretation and identification of micro traces on resharpening flakes are more difficult than performing the same analysis on a complete active tool edge. This is due to a series of factors including 1) the small size of the flakes and difficult handling under the lens of microscopes, 2) the limited area of traces that could be analyzed, 3) the superimposition of technological and functional traces on a limited analyzable area and 4) the dissociation of the resharpening flakes from the original tool's active-edge from which they have been removed. These aspects highlighted by Chan and colleagues 18 were also experienced during our microscopic analysis. The above-mentioned factors have important implications on the distribution patterns of micro-wear on the resharpening flakes. Indeed, we noticed that the location of microwear is, in general, very specific and, in our replica, mostly restricted to the flake's platform ( Supplementary Fig. 15a-f). This aspect certainly reflects the activity of scraping that we performed with the tools, with the ventral face (the striking platform of the resharpening flakes) being most in contact with the worked material. However, we also recorded microwear along the dorsal ridges; although, the texture and the topographical traits of polish were less informative in comparison to those developed on the platforms (Supplementary Fig. 15g). Traces on the dorsal ridges are particularly important when the butt of the resharpening flake is not preserved. Concerning the microwear distribution, we observed that polish develops continuously along the external platform edge of the microflakes (in the luckiest cases), but they may also display a discontinuous arrangement or be not present at all. This was particularly observed when the micro flake under study was not the first one that was removed from the edge of the tool, but rather a "secondary" flake detached on the same spot where the previous one was knapped ( Supplementary  Fig. 16). This can arrive frequently during resharpening, depending on the degree and pattern of the resharpening-retouch. In the case of secondary flakes, the original use edge portion of the tool is retained only on the two lateral extremities of the external platform edge of the micro flake, as shown in Supplementary Fig. 16. However, their interpretation is not always so straightforward, especially when archeological materials are under study. We cannot forget that what was once the ventral face of the tool is now the striking platform of the resharpening flakes. This implies that, along with the use-wear signs, a flake's platform may also retain evidence of the manufacturing traces produced by the contact of the hammer with the stone tool during resharpening. Manufacturing traces are in general quite distinct with a clear directionality of polishes and can be easily distinguished from use-wear traces ( Supplementary Fig. 14a,c, e and 24,51,80 ). Nevertheless, when they overlap with functional traces on a very small portion of the lithic surface (such as on the striking platform) they may hamper the interpretation of functional traces. This is especially true when observing the archeological material because of the presence of other factors that may complicate the microscopic observations (e.g., post-depositional traces). Supplementary Fig. 1. Distribution of the remains recovered so far from the whole excavated area from Schö 13 II-3 (left picture). Detailed drawing of the area where the elephant and most of the finds were found (picture in the middle with the two (+1) refitting pieces). Picture of the elephant bones as they were being excavated (right picture). Drawing: D. Mennella; Photo: J. Lehmann.